Fuel pump for supercharged engines



Aug. 29, 1939. L. T. FOLSOM 2,171,209

FUEL PUMP FOR SUPERCHARGED ENGINES Filed Feb. 28, 1958 It? IZVYENTORPatented Au 29, 1939 UNITED STATES PATENT OFFICE Leon T. Folsom,Berkeley, Calif., 4 assignor to Standard Oil Company of, California, SanFrancisco, Calif., a corporation of Delaware Application February28,1938, Serial No. 192,959

3 Claims.

This invention relates to a fuel pump for internal combustion engines,and particularly to one adapted to supply fuel to a float typecarburetor which is operated under the pressure of supercharged airsupplied to said engine.

There are two general types of supercharging systems as applied togasoline engines. The most common at the present time is that in whichthe carbureted mixture of gasoline and air is compressed after leavingthe carburetor. In the other type the air is compressed before reachingthe carburetor. v

The first type utilizes the ordinary atmospheric carburetor and hascertain constructional advantages as regards mounting of equipment,especially in connection with radial aircraft engines. However, due tothe difficulty encountered in dissipating the heat of compression in thelimited space available there is some-loss of volumetric efficiencywhich is undesirable.

The second type avoids the loss of volumetric efficiency but requiresthe use of a pressure type carbuetor. In such a carburetor the floatbowl is carried at theJnduction line pressure so that metering is stilldependent on depression in the Venturi tube. Such a carburetor must besupplied with fuel at a pressure sufficiently high to produce flow intothe float bowl, but not so high that the float valve cannot shut offagainst it. The limit is reached when the float cannot produce enoughbuoyant force to hold the valve closed. It is evident that any variationin'the' differential pressure between the float bowl and fuel linepressures will result in a corresponding change in the fuel level in thefloat bowl which in turn will result in'a change of mixture ratio.

It is an object of this invention to provide a fuel pump constructionwhich will automatically maintain a predetermined differential pressurebetween the carburetor float bowl and jhe fuel line of an internalcombustion engine for any variation or degree of pressure on the intaketo said carburetor, as for example that caused by a supercharger.

Another object is to provide a fuel pump con- 'struction that willmaintain .a predetermined relation between the fuel line pressure andthe oper-.

I made with change in absolute pressuredueto change in altitude.

Another object is to provide a fuel pump of this nature that is simpleand economical to fabricate] and that will be interchangeable with othertypes without extensive alterations to the engine structure.

These and other objects and advantages will be more fully apparent fromthe following description, and from the attached drawing, which forms apart of this specification and illustrates a preferred embodiment of theinvention.

In the drawing, Figure 1 is a diagrammatic side elevation view of asupercharged engine, with an improvedfuel pump in place thereon.

Figure 2 is a .detail sectional view on line IIII of Figure 1illustrating the details of a fuel pump embodying this invention.

Referring to the drawing, and particularly to the diagram of Figure 1,the reference numeral l8 generally designates an internal combustionengine with a float type carburetor ll attached tothe conventionalintake manifold I2 and supplied with air by a supercharger or blowergenerally designated l3. A fuel tank I4 is provided with an outlet linel5 leading to the fuel pump generally designated l6,fromwhichtheliquidfuel is forced through line H to the float bowl or itsequivalent I8 on carburetor H. A pressure balancing dia: phragm chamberIS in the lower part of the pump 16, to be described in more detailbelow, is fitted with a pressure line 2!] connecting it to thesupercharger outlet 2l which is also the air inlet to carburetor l I, asshown. The usual pressure compensating line 22 is provided fromsupercharger outlet 2| to the top of the float bowl l8.

Referring now to Figure 2, which shows the details of one form of fuelpump embodying this invention, the reference numeral 23 designatesgenerally a part of the engine structure to which the fuel pump 16 maybe secured by any suitable means so that it is in operative relation toa rotating or otherwise moving part of the engine, for example shaft 24provided with a cam or eccentric surface 25. In the upper part of pumpI6 is a conventional pump diaphragm 26 with follower plates 21 and 28secured to a central stud 29. A spring 30 supported in the-body of pumpI6 normally urges the stud 29 and diaphragm 26 upwardly. A cover plate3| is secured to the top of the pump body above-diaphragm 26 to form apump chamber 32 and is provided with a tapped inlet 33 and outlet 34 forthe fuel to be pumped. Conventional inlet and discharge valves of anysuitable typeare provided in the inlet line l5 cured to the bottom ofpump it by cover plate 38 to form the pressure balancing chamber llpreviously mentioned. A tapped connection 42 provides a means ofcommunication from chamber it to the pressure line 23leading to thecarburetor inlet 2!, for a purpose which will be explained in detailbelow.

Intermediate the ends of stud 29 is a reduced section M of suflicientlength to allow the forked end 42 of intermediate lever 43 to engage thestud and yet to have a certain degree of lost motion, for a purposewhich will be apparent. Intermediate lever 63 is hinged on a stationarypin 44, and is actuated by a cam follower lever 45, also pivoted on pinM, and adapted to bear at 48 on cam 25 of shaft 2%. A spring 41 servesto main,- tain lever 55 in contact with its cam 25. Cam follower lever45 is provided with a transverse projection or arm 48, on the oppositeend from cam 25, which projection loosely contacts the upper side ofintermediate lever 43 between its support on pin M and its connection tostud 29 at fork 42. Thus,-as cam 25 is rotated to lift the outer end 46of its follower lever 45, projection 48 will force intermediate lever43, and also stud 29 and diaphragms 26 and 35 downwardly against thespring 30 drawing liquid fuel into chamber 32. As cam 25 turns to itslowest position, as shown, spring 4'! causes cam follower lever 45 tomaintain contact with cam 25, and leaves intermediate lever 43, stud 29and diaphragms 26 and 35 carried thereby, free to be urged upwardlythrough a limited travel by the resultant of the forces exerted byspring 30 and the pressure on diaphragm 35 in chamber l9, to force fuelfrom chamber 32 through line H to float bowl II o carburetor II.

If diaphragms 26 and 35 were of equal area it is evident that thepressurein the fuel line I! will exceed that at point 2i and hence,through line 22, in fioat'chamber l8, by an amount produced by the forceexerted by spring 30, neglecting the pressure drop through the dischargevalve of chamber 32. Since the force exerted by spring 30 issubstantially unvarying, the differential pressure between the fuel lineI! and the car buretor intake 2| will be a constant regardless ofvariations in their absolute values due to supercharging, change inaltitudeor other causes.

By making the diaphragms 26 and 35 of different areas, it would bepossible to make the pressures in the fuel and air lines differ by aconstant amount plus an amountproportional to the absolute values ofpressure in those lines. This, may be expdessed mathematically asfollows:

Let P =fuel pressureabsolu te P,= air pressureabsolute P =pressure inspace between diaphragm absolute A =area of fuel diaphragm A,=area ofair diaphragm F=force exerted by the spring P,A.--P A,+F P A P A; or

In addition to the above, it is obvious that variations in carburetorcharacteristicswith changes in absolute pressure, for example due toaltitude, may be utilized to advantage with this invention to alterair-fuel mixture ratios and similar conditions well known to thoseskilled in the art. Consequently, although a specific embodiment of thisinvention is described and illustrated as applied to a superchargedinternal combustion engine, it is obvious that changes in application,as well as modifications in structure and arrangement can be madewithout departing from the invention, and all such as are within thescope of the appended claims are embraced thereby.

I claim:

1. A pumping device comprising a pump chamber having a movable wall andresilient means adapted to move said wall to decrease the capacity ofsaid chamber, mechanical means for continuously intermittently urgingsaid wall to increase the capacity of said chamber, means forming apressure balancing chamber having a movable wall, means positivelyconnecting said wall with the movable wall of said pump chamber to spacethem an unvarying distance apart, and means adapted to provide anunresticted passage between said pressure balancing chamber and a sourceof fluid pressure acting on the discharge of said pump, so constructedand arranged that variations in said fluid pressure will act in apredetermined manner to modify the force exerted by said resilient meansupon the movable wall of said pump chamber.

2. In combination with an internal combustion engine having an airintake conduit subject to variable pressure, a continuously mechanicallyactuated reciprocating fuel pump for said engine, said pump including aresilient pump diaphragm, a pressure balancing chamber, a diaphragmforming one wall of said chamber, means positively connecting saiddiaphragms to space them an unvarying distance apart, and meansproviding a passage connecting said pressure balancing chamber and saidair intake conduit, so constructed and arranged that variations inpressure in said air intake conduit will modify the discharge pressureof said fuel pump in a predetermined manner.

3. In combination with an internal combustion engine having an airintake conduit subject to variable pressure, a carburetor including afloat bowl, and a continuously mechanically actuated reciprocating pumpadapted to discharge fuel into said float bowl, said pump including aresilient pump diaphragm, a pressure balancing chamber, a diaphragmforming one wall of said chamber, means positively connecting saiddiaphragms to space theman unvarying distance apart, and means providingan unrestricted pressure connection between said pressure balancingchamber, said float bowl, and said air intake conduit.

LEON T. FOLSOML

